Many types of detectors, systems, and methods have been proposed for the purpose of warning of the presence of concealed dangerous weapons, such as handguns. In airports, for example, highly sensitive electromagnetic detectors, such as magnetometers, are being used for screening all on-going passengers to prevent the carrying aboard of concealed weapons such as knives, handguns and other dangerous objects. The luggage and packages being carried aboard are also usually visually inspected by guards, and/or passed through fluoroscopic x-ray detectors and/or other image producing inspection devices for the same purpose.
However, available screening devices and detecting methods require a human interpretation and intervention by trained persons, since conventional metal detectors are often triggered into operation by harmless metal objects, such as keys; and the available x-ray inspection devices often display the presence of shapes having suspicious outward appearances that are later found to be quite harmless objects.
Various commercial establishments including stores, shops, factories, and offices, as well as private dwellings, might also advantageously employ detection devices and systems for warning the occupants of the arrival or presence of visitors carrying dangerous weapons in a concealed manner. However known and available metal detectors, and other such known measuring devices, are not particularly suitable for such uses in being both too expensive for the average home or commercial store, and in requiring the use of reasonably skilled operators to manipulate and use such equipments so as to distinguish harmless objects from concealed dangerous weapons.